The Atomic Energy Regulatory Board (AERB) said on Sunday that there was no heavy water leak in the first unit of the Kaiga Atomic Power Station in Karnataka and that “all plant systems were found to be functioning normally.”
In a press release, Om Pal Singh, Secretary, AERB and Director, Information and Technical Services Division, said an incident of tritium intake by some workers of the Kaiga station was noticed on November 24 during routine sampling of their urine. The AERB deputed two of its officers to the plant and they, along with the plant officials, investigated the incident. A drinking water cooler was found to be the source of water contamination and this cooler was isolated immediately. The tritium contamination was limited to only this cooler. The water tank of this cooler, like other coolers, was kept locked. “However, it appears that some mischief-maker added a small quantity of tritiated heavy water to the cooler, possibly from a heavy water sampling vial, through its overflow tube. Further investigations are in progress in this regard.”
Persons working in the plant were checked and those who were found to have received tritium intake were referred to the hospital for administration of diuretics (which accelerated the process of removal of tritium from the human body by urination). Mr. Om Pal Singh said: “With this, only two persons are having tritium in their body that can cause their annual radiation exposure to marginally exceed the AERB-specified limit of 30 milli-sievert (mSv). All other persons are back to their normal duties. Even in the case of these two persons, further medical management will bring down their potential radiation exposure to less than the AERB-specified limit in a short time.”
He added that the incident was well under control and “there is no cause whatsoever for any radiation safety concern.”
S.K. Jain, Chairman and Managing Director, Nuclear Power Corporation of India Limited (NPCIL), also said he would like to “assure my countrymen that there is no accident” in the Kaiga station and that there had been “no radiation leak from the reactor systems of the first unit there.” About 65 workers of Kaiga-1 receiving radiation doses higher than the prescribed limits “has nothing to do with the reactor’s functioning.”
Kaiga-1 reactor uses natural uranium as fuel and heavy water as both coolant and moderator. Heavy water has two atoms of deuterium and one atom of oxygen. During the reactor’s operation, small quantities of heavy water got converted into tritium, which is in liquid form but highly radioactive.
Asked how “an insider could have played mischief,” Mr. Jain explained that there was heavy water in the reactor’s moderator system and primary heat transporter. Trained workers took out samples of tritiated heavy water from sampling points and carried them to chemical laboratories for analysis. This was done every day. When urine samples of 250 workers were tested on November 24, it came to light that 65 of them had received radiation doses higher than the prescribed limits.
Mr. Jain said: “The radiation workers of the plant are highly experienced people… The computerised access control system has a record of all the personnel who have entered the operating island… But the water in the cooler kept in the service area was found contaminated. We are taking it seriously. We will find out what exactly happened. The punishment for causing the incident will be severe.”